Effect of browned and unbrowned corn products intrinsically labeled with 65Zn on absorption of 65Zn in humans.

Experimental browned and unbrowned corn products were formulated and processed from unenriched, degermed yellow corngrits. The browned product (cornflakes) contained more insoluble dietary fiber and bound more zinc (in vitro) than the unbrowned product (corngrits). During processing some of the cornflakes and corngrits were combined with a small amount of yellow corn endospermhull intrinsically labeled with 65Zn. The intrinsically labeled corn products were fed, in a crossover design, as components of two breakfasts to six normal, unconfined volunteers. Each volunteer absorbed more 65Zn from the corngrits than from the cornflakes. The reduced 65Zn absorption from cornflakes was attributed to heating and toasting reaction products, possibly Maillard, which bound zinc and consequently made the zinc less available for absorption.

Comparison of dietary histories and seven-day food records in a nutritional assessment of older adults.

Dietary histories and seven-day food records were obtained for 54 apparently healthy older adults. The two dietary methods correlated for most nutrients, but mean differences were significant for several nutrients. Intakes below recommended levels occurred most frequently for energy, calcium, and zinc. Biochemical evidence of thiamin and riboflavin deficiency was unexpectedly frequent. Using food records, dietary iron correlated with serum ferritin. Using dietary histories, dietary protein correlated with serum albumin, and dietary zinc correlated with plasma zinc. Using either dietary method, plasma ascorbate was associated positively with both dietary ascorbate and ascorbate supplements, and negatively with cigarette smoking. Use of thiamin- or folate-containing supplements was associated with improved biochemical status for the respective vitamin. Though neither dietary histories nor food records give precise intake data for individuals, either method may be useful for epidemiologic studies with appropriate sample sizes.

Canned foods: appropriate in trace element studies?

This study was conducted to help decrease the variability of metabolic diets. The effects of production lot and storage time on the trace element content of canned food products were compared. Various production lots of peaches, green beans, and tomatoes, canned in tinplate, were purchased and opened at three different times, spaced at 6-month periods. Storage time contributed more to the variability of tomatoes and green beans than production lot. Production lot was the more important factor in peaches. The following guidelines may be useful for metabolic studies lasting more than a few weeks: Use only frozen foods or foods canned in glass, maintaining constant production lots when possible. If only tin-canned products are available, remove the product from the can and freeze when appropriate. When products are retained in the can, maintain storeroom at a low temperature above freezing. In all cases, purchase specifications should require products to be from the most recent canning season, and kitchen procedures should be constant.

Increased cholesterol in plasma in a young man during experimental copper depletion.

Signs of copper depletion were produced in a healthy man by an amount of dietary copper (0.83 mg/day) similar to that in some contemporary diets. Urinary and fecal loss of copper exceeded intake. Plasma copper, ceruloplasmin, and superoxide dismutase activity in erythrocytes decreased. Cholesterol in plasma increased, and hematologic indices were unchanged. Lipid metabolism may be a more sensitive index of copper nutriture than are changes in hematology. The findings support the hypothesis that inadequate copper nutriture or altered copper metabolism contributes to the occurrence of ischemic heart disease.

Effect of oral folic acid supplements on zinc, copper, and iron absorption and excretion.

Effects of folic acid supplements on zinc excretion patterns were seen during studies of mild zinc deficiency in men. During these studies eight men were fed diets containing 150 micrograms of folacin (by analysis) per day. Four of the men were supplemented with 400 micrograms of pteroylglutamic acid (folic acid) every other day. All of the men were fed diets containing about 3.5 mg/Zn per day which were supplemented with 4.0 mg/Zn day for 4 wk and unsupplemented for 16 wk, then supplemented with 30.0 mg/Zn day for 4 wk. Their body weights were kept constant by adjustments of energy intakes and expenditures. Duplicate diets, stools, and urines were analyzed for zinc, copper, and iron. Fecal zinc was significantly (p less than 0.001) higher in the group that received folic acid supplements during the initial control and low zinc intake periods. No significant differences were seen during the period of high zinc intake. During all dietary periods urinary zinc excretion was reduced by about 50% by folic acid supplementation. No apparent changes occurred in iron or copper excretion. These data indicate that supplemental folate influences zinc homeostasis, perhaps through formation of an insoluble chelate and impairment of absorption.

Effect of consuming fiber from corn bran, soy hulls, or apple powder on glucose tolerance and plasma lipids in type II diabetes.

The effects of consuming corn bran, soy hulls, or apple powder on glucose and lipid metabolism were investigated in two studies of persons with type II diabetes. Fiber sources, completely or partially added to bread, were incorporated into subjects' self-selected diets. Low fiber white bread served as a control. In study A, 10 subjects consumed 26 g fiber source daily; in study B, eight subjects consumed 52 g fiber source. Biochemical tests, including a 2-h postprandial glucose test using a low fiber formula meal, were scheduled after 2 and 4 wk of each dietary treatment. Soy hull consumption slightly improved some measures of glucose tolerance, with results varying between the studies. Consumption of 52 g corn bran decreased very low-density lipoprotein cholesterol, triglycerides, and glycosylated Hb, but subject tolerance was poor with the particle size used. Consumption of 52 g apple powder increased low-density lipoprotein and total cholesterol levels.

Influence of type and amount of dietary lipid on plasma lipid concentrations in endurance athletes.

Changes in plasma total cholesterol, triglyceride, and lipoprotein concentrations were assessed in three male endurance cyclists who consumed isoenergetic diets for 28-day periods in which carbohydrate, polyunsaturated fat, or saturated fat contributed about 50% of the daily energy intake. Dietary cholesterol was similar among the diets. Maximal aerobic capacity was maintained at 62 ml O2/(kg X min). Body weights were held within 3% of admission levels. The polyunsaturated fat diet significantly (p less than 0.05) reduced mean fasting plasma total cholesterol in comparison to the saturated fat and carbohydrate diets (160 versus 254 and 243 mg/dl, respectively). Similarly, the polyunsaturated fat diet depressed (p less than 0.05) mean plasma triglycerides relative to the saturated fat and carbohydrate diets (37 versus 62 and 79 mg/dl, respectively). No significant dietary effects were seen on high-density lipoprotein cholesterol. The observed changes in plasma total cholesterol were not significantly different than the values predicted by the Keys' equation, delta CHL = 1.35(2 delta S-delta P) + 1.5 delta Z. We conclude that under controlled conditions in which physical activity is constant l) dietary lipid differences influence fasting serum lipid and lipoprotein concentrations among men with high energy expenditures, and 2) the Keys' equation gives useful predictions of changes in plasma total cholesterol among vigorous men consuming different types and amounts of dietary lipid.

Effect of dietary zinc on whole body surface loss of zinc: impact on estimation of zinc retention by balance method.

Whole-body sweat losses of zinc were studied in men during three separate studies on the effects of marginal intake of zinc. Zinc lost via the sweat appeared to be directly related to dietary zinc intake. Whole body zinc losses of an average of 0.49 mg/day were observed in the men during the control period when zinc intakes averaged 8.3 mg/day. On the other hand, when zinc intakes were 3.6 mg/day, whole body surface zinc losses were substantially lower, averaging 0.24 mg/day in two of the studies and slightly lower than control values in the third study. A loss of 0.62 mg of zinc/day was observed when 33.7 mg of zinc was fed. These losses reduced apparent balances by 12 to 84% and need to be considered when evaluating zinc retention. When men were eating the diets with marginal levels of zinc (3.6 mg/day), zinc losses in sweat gradually declined with time. This suggested a homeostatic mechanism to conserve zinc during periods of depletion.

Folate status of adult males living in a metabolic unit: possible relationships with iron nutriture.

Folate and iron status was monitored at monthly intervals in 40 adult males who were living in a metabolic unit for 2 to 8 months and consuming diets containing 150 to 250 micrograms of folate per day. There were significant (p less than 0.02) declines in hematocrit, serum folate, and serum ferritin. Men who participated in studies for 6 months or more or those with initial serum folate levels more than 10.5 ng/ml and erythrocyte folate levels more than 481 ng/ml also exhibited a highly significant (p less than 0.001) decline in red blood cell folate. Men with erythrocyte folate below 480 ng/ml or serum folate below 10 ng/ml and who participated in the studies for less than 5 months showed little or no change in folate status. The findings may reflect adjustments in body folate to reflect dietary intakes. Also a folate intake of 200 +/- 68 micrograms/day appeared to be adequate for maintenance of folate stores in adult males. A correlation between iron stores and folate status was also observed. However, this relationship may be coincidental.

Effect of a moderate increase in dietary protein on the retention and excretion of Ca, Cu, Fe, Mg, P, and Zn by adult males.

Mineral utilization was studied by metabolic balance techniques in 10 healthy male volunteers fed diets containing 65 and 94 g protein. Both diets contained approximately 650 mg calcium, 1 mg copper, 16 mg iron, 250 mg magnesium 1000 mg phosphorus, and 7 mg zinc. The diet consisted of conventional foods; the additional 29 g protein was egg white protein mixed into a beverage and fed twice per day. Plasma mineral levels were not affected by the increase in dietary protein. When the diet provided 94 g of protein, urinary calcium and zinc were slightly, but significantly, increased by an average of 35 mg (p less than 0.05) and 0.15 mg (p less than 0.001), respectively. Apparent mineral absorption and balance were unchanged by this modest increase in dietary protein.

Dietary fiber and personality factors as determinants of stool output.

We examined effects of fiber on stool output, since this is one of the primary mediating variables for the hypothesized relationship between fiber and disease. Total neutral detergent fiber in the dietary fiber source was predictive of stool weight but not frequency. Substantial individual differences in stool output remained when dietary factors were controlled. Personality measures were used to predict stool weight and frequency independently of diet, and accounted for about as much variance in stool output as did dietary fiber. These results suggest that personality factors predispose some persons to low stool output. These individuals may benefit particularly from dietary fiber.

Accuracy of predictions of long-term energy needs.

Energy needs as estimated by various methods were compared restrospectively with actual energy needs of eleven subjects who participated in long-term metabolic studies. Eight methods were compared with actual energy needs. The most satisfactory were the Harris and Benedict formula, the Kleiber formula, and the Mayo Foundation Nomogram, with an additional percentage allowed for activity energy. Interviewing methods were the least satisfactory for estimating energy needs. None of the methods was satisfactory for long-term use with individuals, indicating the necessity of follow-up and adjustment when energy intake is externally controlled.

The effect of parity and time between pregnancies on maternal hair chromium concentration.

Values for hair chromium concentration of nulliparous women and parous women who had just given birth to a child were determined by atomic absorption spectrophotometry. Mean values for hair chromium concentration of nulliparous and parous subjects were 309 +/- 23 and 117 +/- 10 ppb, respectively. The difference was highly significant (P less than 0.001). No further significant decrease in hair chromium was observed in women who had borne more than one child. Hair chromium concentration increased significantly with the amount of time between pregnancies, especially when at least 4 years had passed since the end of the last pregnancy (P less than 0.001). These data suggest a state of suboptimal chromium nutrition during pregnancy.